Effect of phage lysin on infection and biofilm formation in rabbit after knee joint prosthesis implantation

Objective To investigate the effect of local injection of phage lyase LysGH15 into rabbits’knee joint on the systemic inflammation, local infection around knee joint prosthesis and biofilm formation on the prosthesis surface after their knee joint prosthesis implantation surgeries. Methods Models of Staphylococcus aureus infection on rabbits’ knee joint prosthesis after prosthesis implantation were built and divided into experimental group for intra-articular injection with lyase and control group for injection with saline into their joint cavity. The phage lysin LysGH15 was synthesized and purified. On the 1st, 2nd and 3rd day after the inoculation with Staphylococcus aureus bacteria into the rabbits’ knee joint cavity of the prosthesis implanted side, 0.5 ml diluted solution of LysGH15 was injected into the knee joint cavity with infection around the prosthesis for the experimental group rabbits and 0.5 ml saline was injected into the corresponding joint cavity for control group rabbits as blank contrast. On the 1st, 3rd, 7th and 14th day, blood samples were collected from their ear vein to make plasma procalcitonin test for evaluation of rabbits’ systemic infection. After the last time for collection of venous blood samples, these rabbits were killed instantly and their knee joints of prosthesis implantation side were dissociated. Tissue around the prosthesis was processed with HE staining to observe and evaluate the local infection and tissue necrosis around the prosthesis. The biofilm formation on the prosthesis surface was evaluated with semi quantitative method after the observation of samples under scanning electron microscope (SEM). Results After the injection of LysGH15 in experimental group, their serum procalcitonin level, which worked as the systemic inflammatory marker, decreased rapidly especially on the 3rd day after lysin injection. Compared with the control group, the infection degree of experimental group significantly decreased. In the experimental group, the infection and necrosis degree of the tissue surrounding the prosthesis were significantly lower in the experimental group than those in the control group. The semi quantitative scores were conducted for these samples and graded to make rank sum test. The difference between the two groups was statistically significant (U=2.4948, P=0.0126). There was a statistically significant difference in the rank sum test between the two groups in the quality of biofilm formation (U=2.2539, P=0.0242). Conclusion Phage lysin LysGH15 can alleviate the rabbits' systemic inflammation caused by Staphylococcus aureus bacteria after their knee joint prosthesis implantation, reduce the extent of damage caused by infection and inflammation to the tissue around the prosthesis, and inhibit the formation of bacterial biofilm on the surface of implanted prosthesis. Key words: Rabbits; Knee joint; Bacteriophages; Biofilms; Prosthesis-related infections; Staphylococcus aureus